SRA

Most investigations of crop salinity tolerance are conducted on the basis of short-term stress condition within one growth stage. Understanding of crop response mechanisms to the long-term salinity stress (LSS) will be more valuable for improvement of crop salinity tolerance than that of short-term stress. Hence, we treated allohexaploid wheat seeds with a LSS condition cross germination and seedling stages for 30 days. To elucidate comprehensive gene expression and physiological response strategies of allohexaploid wheat to LSS, we analyzed the chloroplast ultrastructure, anatomy, plant hormones, organic compatible solutes, inorganic ions, and transcriptomic profiling of the stressed plants. The global transcriptomic profiling and biochemical measurements showed that energy partitioning between general metabolism maintenance and stress response may be crucial for survival of allohexaploid wheat under LSS. Under LSS, wheat might shift energy form general maintenance to stress response thr allohexaploid ough enhancing ABA pathways, and suppressing GA and JA pathways in leaf. We further distinguished the expression status of A, B, and D homoeologs of any gene traid, and surveyed effects of LSS on the homoeolog expression bias for salinity tolerant triads. We found LSS has similar effect on expression of three homoeologs (A, B, and D) for most salinity tolerant triads. However, in some salinity tolerant triads, LSS imposed different effects on expression of three homoeologs. We searched three key salinity responsive elements (ABREs, DRE1, dehydration responsive element) in promoter regions of A, B, D homoeologs of all 149 salinity tolerance triads. Only 48 salinity tolerant triads contain ARBEs or DRE1 in their promoter. Of these 48 salinity tolerant triads, only in four salinity tolerant triads three homoeologs showed same salinity responsive element composition, in other 44 salinity tolerant triads three homoeologs contained different salinity responsive element elements in their promoter regions. We propose that, for these salinity tolerant triads, expression of three homoeologs may be modulated by different mechanisms. The Cis-acting element divergence among three homoeologs may incur their different responses to LSS.